In the manufacture of semiconductor integrated circuits (hereinafter abbreviated as ICs), various functions are provided by forming active elements such as CMOSs and bipolar transistors and passive elements such as resistors and capacitors on wafers, and by providing metal wiring which connects them, thereby the process of manufacturing the wafers is completed. After the completion of the wafer manufacturing process, a test to check the quality of IC products, that is, a so-called wafer test is conducted in wafer form before dicing (cutting). In the wafer test, ICs, which have met preset characteristic specifications, are selected, but ICs, which have not met the characteristic specifications, are rejected and thrown away. The characteristic specifications are set in a certain permissible range in consideration of the purpose in the use of ICs and so on.
In recent years, however, to enhance the sensitivity to sensing signals of ICs for sensors or the conversion efficiency of ICs for power conversion, wafer tests to obtain high-quality ICs have been conducted by narrowing the permissible range of the characteristic specifications to the extent possible. But when wafer tests have been conducted by narrowing the permissible range of the characteristic specifications, ICs manufactured by using conventional semiconductor device manufacturing methods have increased in the number of defectives to be rejected, which has resulted in their increased production cost.
Therefore, to produce IC products, which meet the permissible range of the characteristic specifications by adjusting (trimming) the characteristic values of the ICs which have not met the characteristic specifications after the wafer tests, will become a more important and essential technique from now on. Because of this, various “trimming techniques” have been proposed. Typical “trimming techniques” includes “laser trimming” in which part of wiring is cut by using laser beams, “Zener zapping” in which Zener diodes are subjected to avalanche breakdown to form filaments for wiring, “digital trimming” in which digital data is written into memory elements to adjust circuit characteristics, and “wiring formation trimming” in which wiring of electric circuits is newly formed.
Although such various techniques have been proposed as “trimming techniques” used after wafer tests as described above, there is a need to use an expensive apparatus in the trimming process and to form elements and circuits for trimming, which are very likely to become unnecessary, on wafers in advance. As a result, the conventional trimming techniques have caused the problem that the production cost of ICs is increased.
Moreover, in “wiring formation trimming”, special drawing patterns are formed in the form of thin films according to the results of wafer tests, and the thin films are affixed to the corresponding spots of the wafers to form wiring for trimming (see, for example, JP-A No. 5-291258). However, in this trimming technique, it is very difficult to form wiring with high accuracy, and high-quality ICs can not be manufactured with high yields.
Furthermore, as “wiring formation trimming”, a trimming technique has been proposed in which openings where electrode terminals are exposed are formed on wafers in advance, metal paste is applied to the corresponding openings during trimming to connect the desired electrode terminals with each other, and shielding resin is applied on the connection spots (see, for example, JP-A No. 2004-273679). However, in such conventional “wiring formation trimming”, since the metal paste is applied onto the desired electrode terminals in such a way that a certain wide area is covered to form metal paste layers for the formation of electric connection, it has been difficult to perform a fine adjustment. In addition, to prevent the metal paste layers, which have been formed through the application onto the electrode terminals, from peeling and so on, shielding resin layers must be formed on the upper portions of the metal paste layers and hence, ICs have not been easy to manufacture, which has brought about a complex manufacturing process.